Many developments have already been disclosed with regard to polymers containing terminal functional groups. For example, a number of methods are already known which can attach a functional group to the terminal of the molecule of liquid rubber or polybutadiene by the use of an anionic polymerization technique. For instance, Japanese Patent Application Kokoku (Post-Exam. Publn.) Nos. S190/62, 342/63, 23,043/63, 24,174/67 and 15,108/71 disclose processes for producing terminal functional group-containing polymers by treating polymers polymerized by use of an organolithium compound etc. with carbon dioxide, epoxy compounds, thioepoxy compounds etc.
Further, U.S. Pat. No. 3,471,431 discloses a terminal-sulfonated polymer obtained by the reaction of a block copolymer with a sultone. U.S. Pat. Nos. 3,838,108 and 4,070,344 disclose amine-terminal polymers obtained by reacting polyisocyanate or polyisothiocyanate to the terminal of a living polymer. U.S. Pat. No. 4,244,862 discloses a coating composition and a printing ink composition which comprise a polymer containing a terminal polar group obtained by treating a living polymer of a block copolymer with a polar group-containing compound and an inorganic pigment compounded therewith. U.S. Pat. Nos. 4,020,036 and 4,330,449 disclose compositions comprising a block copolymer having a carboxyl group at the polymer terminal compounded with a thermosetting unsaturated polyester or asphalt.
As to the applications of styrene/butadiene block copolymers and styrene/isoprene block copolymers, particularly as to their use as tackifier compositions, water absorbing compositions, thermoplastic compositions, and electroconductive compositions, the following techniques have been disclosed.
Pressure sensitive adhesive agents have hitherto been used in various applications including pressure sensitive adhesive tapes and labels. The adhesive agent is applied onto tapes or the like materials generally by coating the solution of the adhesive agent in a solvent on a substrate by such means as a roll or spray. However, the use of solvents involves many problems from the viewpoints of atmospheric pollution, fire, industrial environmental hygiene, etc., which have been viewed as serious social problems in recent years. As a result, a hot melt pressure sensitive adhesive agent of the solventless type has recently attracted attention as a means for obviating such difficulties.
A variety of polymers are used as the base polymer of the hot melt adhesive, including ethylene-vinyl acetate copolymers, block copolymers comprising conjugated dienes and vinyl aromatic hydrocarbon compounds, ethylene .alpha.-olefin copolymers and polyester resins. Particularly, the block copolymers tend to be preferably used because they show a fairly good balance between tackiness and creep resistance. For example, Japanese Patent Application Kokoku (Post-Exam. Publn.) Nos. 17,037/69 and 41,518/70 disclose adhesive compositions comprising such linear block copolymers as polystyrene-polybutadiene-polystyrene or polystyrene-polyisoprene-polystyrene. Japanese Patent Application Kokoku (Post-Exam. Publn.) No. 49,958/81 discloses a hot-melt type adhesive composition using a branched block copolymer, (polystyrene-polybutadiene) .sub.n X.
Further, rubber compositions formed by compounding natural or synthetic rubber with polyvinyl alcohol, polyacrylic acid salts, carboxymethylcellulose, hydroxyethylcellulose and the like each added as a water absorbing substance are disclosed, for example, in Japanese Patent Application Kokai (Laid-Open) Nos. 143,653/78, 7,461/79, 7,463/79 and 20,066/79. They are useful as water-swelling materials, such as water-stopping materials, in the field of civil engineering, construction, etc. since they absorb water and expand.
However, since conventional water-swelling materials employ natural rubber or usual synthetic rubber as the rubber component, the compounds require a vulcanization operation using sulfur, peroxides or the like substances, which makes their fabrication complicated. In order to obviate such difficulties, attempts have been made to incorporate a water absorbing substance into a thermoplastic elastomer which has at room temperature an elasticity similar to that of vulcanized natural or synthetic rubber without being vulcanized and yet shows at a high temperature a processability similar to that of thermoplastic resin. For example, Japanese Patent Application Kokoku (Post-Exam. Publn.) No. 41,092/85 discloses a composition which comprises a thermoplastic elastomer formed out of styrene and butadiene compounded with a water-swelling solid crosslinked product of a copolymer of lower olefin and maleic anhydride.
In using high molecular substances as the material of fiber, film, sheets, molded articles, etc., when the use of a single high molecular substance is unsatisfactory for the object of the product, many attempts have been made to give satisfactory strength, to improve processability, or to reduce the cost of the product by forming a composition comprising a number of components or forming a laminate. However, when different kinds of high molecular substances are mixed into a composition, the number of combinations obtainable is rather small which shows a good compatibility.
Mixed compositions of different kinds of high molecular substances with poor compatibility often fall to attain the improvement in properties intended by the mixing because of a lack of homogeneity and peeling between different phases which are caused by poor miscibility.
It is well known that styrene-butadiene block copolymer, styrene-isoprene block copolymer, and like polymers are used as one component to obtain a composition with excellent properties by mixing high molecular substances. Examples of such methods are disclosed, for example, in Japanese Patent Application Kokai (Laid-Open) Nos. 11,486/72, 66, 743/74, 75,651/75, 126,255/79, 10,542/81, 62,847/81 and 100,840/81.
As to the method for imparting electroconductivity to elastomers and thermoplastic resins, there are known those methods which comprises incorporating thereto electroconductive materials such as carbon black, graphite powder, metal powder, and metal fiber. Since the range of conductivity of the electroconductive composition obtained by such methods can be controlled according to the kind, shape and compounded amount of the electroconductive material used therein, such compositions are widely used, as an antistatic material or an electroconductive material depending on their level of electroconductivity, in antistatic carpets, ruggs, flooring, shoe soles, medical rubber goods, electromagnetic interference materials, and so forth.
Electroconductive elastomers mainly used at present are those which comprise principally silicone rubber or fluorosilicone rubber. However, a strong need is present for materials which are less expensive and better in processability as electroconductive materials become more widely used. Under such situations, block copolymers of butadiene or isoprene and styrene are attracting attention as the raw material for electroconductive materials because when the styrene content is low they have at ordinary temperature a similar elasticity to that of vulcanized natural or synthetic rubber even without being vulcanized and at high temperature they can be fabricated similarly to conventional thermoplastic resins, whereas when the styrene content is high they nave properties of thermoplastic resins excellent in impact resistance. For example, Japanese Patent Application Kokai (Laid-Open) No. 16,558/79 discloses an electroconductive plastic composition comprising a thermoplastic radial teleblock copolymer of butadiene and styrene compounded with carbon black.